Loudspeakers are generally passive complex loads connected to an audio amplifier by standardized two-wire load speaker wiring designed to carry high-voltage, high-current analog signals in the audio frequency band. Some loudspeakers can be powered, that is have an external power source and powered components, such as a subwoofer with an internal amplifier, but these too are generally connected to the audio source by a two-wire connector which delivers the audio signal to be reproduced. As wired loudspeakers are seen as passive system components with fixed load characteristics, there has not been any need to communicate or pass data and control signals between the amplifier and the loudspeaker.
Some technologies are emerging that would make it desirable to have a communication path between a loudspeaker and the amplifier. An example of such a technology is described in U.S. patent application Ser. No. 12/908,773 by Butler, which is hereby incorporated by reference. The system described in the Butler application provides for a mechanism at the loudspeaker to attenuate the audio signal in over-voltage, over-current or other over-limit conditions. The mechanism also allows for the attenuation of the audio signal for artistic or logistics reasons, such as varying the strength of the audio signal to each speaker in a bank of speakers, even if there is no threat to the loudspeaker.
In the system described in Butler, loudspeakers equipped with digital attenuators have the intelligence to digitally attenuate the AC input signal, monitor voltage, electrical current, temperature, frequency, cone movement, and/or other limiting values. Such intelligent loudspeakers can benefit greatly from the present invention wherein the monitored values and attenuation characteristics can be communicated to a remote device or devices residing elsewhere in the loudspeaker wiring path. For example, the intelligent loudspeaker equipped with digital attenuation and limit monitoring can pass the monitored values and/or attenuator settings to remote devices, which in turn can change the parameters of the digital attenuator from afar. This can be beneficial in systems where a user desires to attenuate a specific speaker which resides in a chain of connected loudspeakers or the user simply wishes to monitor the performance and characteristics of a specific loudspeaker from afar.
Other applications wherein a transparent digital communication system for use within passive, un-powered loudspeakers can be beneficial include, but are not limited to: audio systems that utilize Digital Signal Processors (DSP) for loudspeaker processing and equalization, and audio systems that require advanced status monitoring and/or diagnostic support. Audio systems that utilize DSP for loudspeaker processing and equalization can benefit from the present invention by receiving an electronic identification from the un-powered loudspeakers. Once the DSP has received the loudspeakers identification (make, model, serial number, etc.), the DSP can automatically recall the appropriate signal processing algorithms required for that specific loudspeaker. For example, many modem professional audio amplifiers contain on-board DSP processors that provide the user with a host of signal processing tools such as filtration, delay, gain, phase shifting, etc.; however, the user must configure the DSP parameters for the loudspeaker connected thereto. By incorporating the invention disclosed herein, the properly equipped loudspeaker can identify itself to the amplifier and DSP processor, thereby allowing immediate recall of the correct DSP parameters. This provides a “plug- and play” capability not seen before with un-powered loudspeakers.
Another general application for the present invention is within audio systems requiring status monitoring and/or diagnostic support. In such systems, the audio designer desires to monitor as many audio components as possible, thereby providing a more comprehensive understanding of the operating conditions of each component within the overall system. In the past, un-powered loudspeakers have not provided any mechanisms for status monitoring. By applying the present invention, un-powered loudspeakers can now broadcast loudspeaker status and other performance characteristics to remote devices residing on the loudspeaker wiring. These remote devices can display the information via a computer interface and/or a local user interface. Though not limited to, the present invention can be used to pass diagnostic information such as driver temperature, voltage, current, cable phase, and/or impedance. This information can be invaluable to system operators, contractors, and installers while operating, installing, and/or commissioning an audio system.